The background of this invention resides within self-contained breathing apparatus which use a second stage or demand regulator. Such demand regulators have been known to utilize a diaphragm. The diaphragm is balanced between ambient pressure and pressure within the regulator. When pressure within the regulator is diminished by a diver's inhalation, the diaphragm moves and the regulator proceeds to function.
Movement of the regulator diaphragm generally causes a contacting levers, toggle, or other movable actuating member to move in response to the diaphragm. When such movement takes place, the movable member in contact with the diaphragm is moved in a manner to cause a valve or other sealing member to unseat. When the valve or other member unseats, it causes a flow of breathing gas such as compressed air from a source of high pressure regulated gas. Such high pressure regulated gas can be provided from a tank and first stage regulator.
Such demand or second stage regulators are known in the art for both divers and self-contained breathing apparatus for use with industrial and fire safety equipment. Most of them have an indigenous problem of rapid flow upon the valve opening. Fundamentally what happens is after the valve or means for valving the intermediate pressure initially takes place, the air or breathing gas then flows through the valve seat area more readily than it initially flows.
First of all, flow across the valve seat increases merely by opening and pressure pushing it after it has been unseated. Secondly, the air or breathing gas once it passes initially through the valve, creates a venturi effect within the regulator housing which causes a pressure drop and helps to draw down the diaphragm that contacts the lever which further opens the valve. This is in effect a valve opening enhancement function from the standpoint of overcoming spring pressure on the valve.
The valve is initially caused to move by the mechanical action, and is caused to move further by a second mechanical action. An idealization is to allow a greater mechanical advantage initially in the movement until the venturi or imbalance takes over and then provide a lesser mechanical advantage thereafter to move the valve.
The inhalation effort required to move the valve firstly is greater than the inhalation effort required to move it the remaining portion of movement. This is due to the fact that after initially opening, the venturi acting on the diaphragm and the imbalance across the valve draws it into a further opened position with greater ease. Generally, the internal design of the regulator should cause a near balance between the valve spring that closes the valve and the venturi effect and flow imbalance across the valve so that the regulator requires a minimal inhalation effort to sustain any particular flow that the user requires. Consequently, with regard to diaphragmatically operated second stage regulators, it would be preferable to have a greater mechanical advantage at the beginning of the movement and then subsequently a lesser mechanical advantage.
Such action creates an easier breathing regulator, inasmuch as less suction or inhalation is required due to greater mechanical advantage. After the initial opening, the lesser mechanical advantage allows for a smoother operation without a rush of air to the diver.
This invention solves the problem of the initial mechanical advantage being required in a greater magnitude through its unique lever system. The lever's contact of the poppet assembly, to cause it to move and open the valve, is incorporated within an enhanced angular orientation for greater mechanical advantage during initial movement. The poppet assembly is then moved with less mechanical advantage after initial opening when the air starts to pass through the valve and creates a venturi within the regulator housing acting on the diaphragm to push down the lever which increases the valve opening. This is caused by the lever at its opposite end from the diaphragm being provided with a first angle or contact point of engagement which is closer to the axis of rotation of the lever at its contact point for movement of the poppet assembly. The subsequent movement allows the placement of the contact point to be removed to a farther position from the axis of rotation. This creates a longer point of contact from the center of the radius of movement thereby causing greater effort, inasmuch as the mechanical advantage is reduced by the increased distance from the radius of movement.
Another drawback of the prior art is that the relative size of second stage regulators is generally large due to overall exhaust valve configurations. This invention overcomes the exhaust valve placement problem by creating two purge valves in an optimum position.
In particular, exhaust or purge valves in the past have been displaced from the main body of the second stage regulator to a significant degree. This is due to the fact that they were in the form of one large exhaust valve or in the alternative, two smaller valves which had to be placed in a removed location from the center of the regulator body.
This invention overcomes this deficiency by allowing angular placement for minimum cubic displacement. The angular placement places the exhaust valves in close proximity to the regulator valve body to provide for minimally sized orientation of the respective valves and regulator cubic displacement in which they are seated.
Another disadvantage of the prior art is that the delivery of breathing gas from the valve body oftentimes took place in an offset location. This invention allows for a delivery of breathing gas in a centrally oriented outlet with respect to the user's mouthpiece. When taken in consideration of the enhanced operation, this is an improvement in combination with the other portions of this invention.
Finally, an inventive consideration with respect to the structure of this second stage regulator appertains to the utilization of an easily removable cover for the exhaust valves. In the past, covers have not been readily removed from the exhaust valves for checking of such exhaust and purge valves. This invention allows a snap-on or tab and groove securement relationship for the cover. The tab and groove relationship is enhanced by the spring characteristics of the cover. It can be snapped into grooves and removed on a ready basis without the requirement of special tools and/or disassembling of the entire regulator to access the exhaust or purge valves.
Consequently, it is believed that this invention has numerous inventive characteristics attendant therewith both in their singular orientation and when taken in combination with each other.